Preparation of alkyl sulphates from liquid olefines



July'l4, 1936'. H. s. YOUNG" 7, PREPARATION OF ALKYL SULPHATES FROM LIQUID OLEFINES Filed Dec. "r, 1935 T INVENTOR.

Howard 5.901427 ATTORNEY.

July 14, 193

PATENT orrics PREPARATION OF ALKYL SULPHATES v FROM LIQUID OLEFINES Howard S. a Young, Wilmington, Del., assignor to E. I. du Bent de Nemours & Company, Wilmington, Del., a corporation of Delaware Application December 7,1933, Serial No. 701,336 14 Claims (01. zen-99.12)

This invention relates to the art of producing alkyl sulphates and more particularly to the preparation of alkyl sulphates from liquid olefines. It is well known that alkyl sulphates such as ethyl, propyl, and butyl sulphuric acids may be prepared by the absorption of the corresponding gaseous olefines in sulphuric acids of varying strengths. It is further known that these absorptions are accelerated by the catalytic action of certain metallic salts in the absorbing acid.

This invention has as an object the provision of an especially advantageous process for converting liquid olefines andsulphuric acid to alkyl sulphates. Another object is the provision of a process whereby liquid propylene or liquid hydrocarbon mixtures rich in propylene may be converted into isopropyl sulphuric acid and di-isopropyl sulphate. A further object is the provision of a process by means of which the above objects may be advantageously accomplished in a simple continuous and economical manner with the use of apparatus of relatively simple construction.

These objects are accomplished by the following invention wherein liquid olefines or liquid hydrocarbon mixtures rich in propylene are pumped with sulphuric acid at moderate temperatures and pressure through a coil or bank of tubing of diameter small in relation to its length, with adequate provision for dissipating the heat of the reaction.

In the'accompanying drawing Figure 1 represents an apparatus suitable for the processes of the present invention. Figures 2 and 3 represent jacketed reaction coils suitable in the present process and more specifically referredto below.

Liquid propylene from reservoir T1 is pumped by pump P1 thru pipe A1 and sulphuric acid from reservoir T2 is pumped by pump P2 thru pipe A2 into coil C maintained at a regulated temperature in the bath D. In coil C the reaction takes place and the reaction products are forced thru pipe E and let off valve G into separator H. The gauge F serves to indicate the pressure in the pipe. Waste gases are vented from p separator H thru pipe J or sent to a compressor or the like.

The isopropyl sulphate reaction product is taken all from separator H thru pipe I and stored in reservoir K from which it may be drawn off for hydrolysis, etc. thru valve V4. The isopropyl. sulphate may be pumped by means of pump P3 thru line L back into coil '0 for purposes of re cycling, as is indicated hereafter.

Preferred embodiments of the invention are- 5 set forth in the following examples which are column to remove the unreacted gases.

presented for purposes of illustration but are not to be regarded as limitative.

Example 1.A mixture of 93% sulphuric acid and a liquid hydrocarbon mixture containing 95% propylene is passed through a coil made' 5 from 35 ft. of steel tubing of A;th inch internal diameter and Ath inch external diameter. The mixing of the liquids is effected in a steel T directly connected to the top of the reaction coil. The pr'essure'within the'coil is controlled from 10 200 to 400 lbs. per sq. inch gauge by a let-down valve at its end and its temperature is maintained at 0-+5 C. by immersion in an ice bath. The hourly addition rates of sulphuric acid and liquid hydrocarbon mixture are 671 and 312 grams, re- 15 spectively, and give a substantially equimolal, mixture of the reactants. After reduction of pressure to atmospheric, the reaction products are passed into a separating column from which 939 grams of clear liquid and 45-50 grs..of gas 20 (about 50% propylene) are obtained per hour. The liquid has a specific gravity of 1.30 and contains 28.6% propylene in the form of isopropyl sulphates.

Hydrolysis of the liquid by dilution with ap- 25 proximately 1 kg. of ice water followed by distillation yields over 90% of the olefines as isopropyl I alcohol.

Example 2.Sulphuric acid of 93% strength and a liquid hydrocarbon mixturev containing 30 90% propylene are passed through a steel reaction coil at rates of 57 lbs. and 27.8 lbs. per hour respectively. The inside diameter of the tubing of the reaction coil is 0.20 inch and the outside diameter 0.38 inch. The tubing in the coil is 35 650 ft. long and the coil is surrounded by an efiicient cooling jacket such as is shown schematically in Figure 2. The temperature of the reaction mixture is held at 20 to 25 C. by regulation of the rate of flow of the cooling medium (in this 40 case water) and the pressure within the coil is maintained at 250350 lbs. per sq. in. by adjustment of a relief valve at the end of the coil.' The reaction products after reduction to nearly atmospheric pressure are passed into a separating 45 Seventynine lbs. per hour per liquid product is withdrawn from this separator. This liquid is almost colorless after a specific gravity of 1.30 and on hydrolysis yields 29 lbs. of isopropyl alcohol. 50

The crude isopropyl sulphates produced as described in the above examples may be passed directly from the separators into suitable apparatus for their continuous hydrolysis to sulphuric acid and to the binary of isopropyl alcohol with merized olefines.

water. The crude isopropyl alcohol binary from the continuous hydrolysis may in turn be introduced after vaporization, together with air, into a hot tube containing silver gauze catalyst wherein the isopropyl alcohol vapors are converted to acetone as is fully described in the copending application of J. W. Woolcock, Serial No. 683,320 filed August 2, 1933. By employing the three step process above described propylene may be continuously converted into acetone in a highly efllcient and economical manner. V

The temperature at which the reaction is maintained is an important factor in the success of the process of this invention. Temperatures somewhat below 0 C., that is, 0 to 15 C. may be employed but require extensive refrigeration and because of the increased viscosity of the sulphuric acid at low temperatures require additional power for pumping the liquid into the coil or bank of tubing to overcome the excessive pressure drop. Temperatures much in excess of 30 C. are to be avoided inasmuch as the products obtained at these temperatures contain poly- Thus the products obtained at 50 C. are dark brown in color and contain free sulphur dioxide and a considerable amount of a dark heavy oil. While the process may be carried out at temperatures ranging from 10-+40 C., temperatures in the neighborhood of 25 C. are greatly preferred because of the procedural advantages of cooling with water.

Only moderately high pressures are required for the processes of this invention. The lower limit of pressure is defined by the vapor'pressure of the olefines at the reaction temperature. Thus, at 25 C. the pressure in the case of liquid propylene is approximately 160465 lbs. per sq. in. gauge. The upper pressure limit is determined only by the pressures which the apparatus will withstand. Pressures of 200-400 lbs. per sq. in. are preferred in this process.

The heat of reaction of liquid propylene and sulphuric acid is high and it is important that proper means be provided so that the temperatures above given may be maintained and that no local over-heating will occur in the reaction mixture. The methods employed for the adquate dissipation of heat will depend largely on the conditions of flow in the reaction tubing. In the above examples the two immiscible fluids, liquid propylene and sulphuric acid, are pumped through the reaction tube at an average velocity low enough so. that straight line flow occurs in both phases, and the interface between the phases is continuous. Under conditions of straight line flow in tube of relatively small diameter, reaction takes place at such a rate ,that the heat produced may be satisfactorily removed and the reaction temperature properly controlled by immersing the tube in a cooling bath maintained at the desired temperature. Conditions of straight line fiow are preferred when the reaction is carried out on a small scale, but as the output is increased it becomes necessary either to use a tube of greater cross-section and greater length, or to use a bank of tubes operating in parallel. Therefore, for increased production, it is desirable to increase the velocity of. the reactants to obtain turbulent flow in which the extended surface interface per unit volume is much higher than in viscous flow. Under conditions of turbulent flow it is more difllcult to provide adequate cooling but it may be succcessfully accomplished in many ways, for example, by refrigeration, by introduction of the reactants at various points along the reaction tube to avoid local over-heating, as is shown in Figure 3 of the drawing, or by recycling of a portion of the isopropyl sulphate which in this way acts as a solvent for both sulphuric propylene and as a diluent for the reac- 5 tion mixture so that the heat evolved is not excessive. This is shown in Figure 1 wherein the isopropypl sulphate is recycled thru pipe L by means of pump P3.- This recycling pipe L may be out in or cut out of the system by valves V3 and 10 V5. Various mechanical means maralso be used to dissipate the heat from the turbulent flow mixture. Thus, the reaction mixture may flow within a pipe within which a second pipe is placed through which a cooling medium is pumped.

It has been found that the time required for reaction between the sulphuric acid and the liquid propylene is appreciable, and the reaction tube or pipe must be of suiiicient length to allow completion of the reaction at the rate of flow em- 20 ployed. The length of the reaction pipe will also depend upon the conditions of flow employed, greater length being necessary for viscous flow than turbulent flow. .The proper length required for a given set of conditions may be readily de- 25 termined by experiment. It is diificult to calculate in advance in view of the fact that the characteristics of the fluid within the reaction tube changeas the reaction proceeds, thereby making it difllcult to apply available data such as Reyn- 30 olds numbers.

The entrance arrangements of the reaction mixture to the reaction tube are not limited to those described in the above examples and any suitable means may be employed. The react- 35 ants should, however, not be mixed too soon before their entrance to the cooled reaction tubes since reaction should not be effected before the cooling effect is available. In the above examples steel tubing was used but any other material of suflicient mechanical strength, sufflcient resistance to the corrosive action of the reactants and having good qualities of heat transfer is satisfactory.

In the examples the liquid hydrocarbon is 45 propylene. Other liquid olefinic hydrocarbons or mixtures of liquid olefinic hydrocarbons may be used. A higher pressure or a lower temperature is required for ethylene, a lower pressure or a higher temperature for butylene and the like. 50 Sulphuric acid of 93% is employed in the above examples. Sulphuric acid of concentrations varying from to 100% may be used. Liquid propylene reacts very slowly with acids weaker than 75% andthe use of these acids is not practical 5 under the conditions outlined. The use of concentrated sulphuric acid (over 95%) is feasible but owing to the. extreme rapidity with which acids of such concentration react with-the olefines, the cooling medium must be applied at a 60 very high rate to avoid polymer formation. Preferred concentration is in the range of -95%.

'High conversions of the reactant presentv in the drolysis and distillation.

The equipment required for the process of this invention .is relatively simple in its construction 75 and the process is simple, practical and economical in operation. The solution of alkyl sulphate; for example isopropyl sulphate, obtained in the process of the present invention may be reacted with water to form alcohols, for example isopropyl alcohol or may be reacted with acids such as acetic acid to give the corresponding esters.

The reaction between liquid oleiines and sulphuric acid effected by pipe-line mixing affords a manifold decrease in reaction time and a material reduction in equipment size as well as af-.' fording an elimination of the formation of polymers. To. the absence of the usual side reaction such as oxidation and polymerization is ascribed the formation of a superior product almost waterwhite in color from which nearly theoretical recoveries of alcohols such as isopropyl alcohol may be obtained on hydrolysis.

The word "concurrent" as used in the specification andclaims is usedin the etymological sense of flowing in the same directiom As many apparently widely different embodiments of this invention may be made without de- Earting from the spirit and scope thereof, it is be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

I claim: Y

1. Process for the preparation of alkyl sulphates, which comprises forcing a liquefied olefin and sulphuric acid of -100% concentration concurrently and continuously thru a flow path of restricted cross-section while maintaining the temperature of the reactants below 40 C.. the length of said flow-path being adjusted so that the reaction is .substantially completed within said flow-path.

2. Process 0! claim 1 in which the reactants are maintained at a temperature not above 30 C. 3. Process of claim 1 in which the molecular ratio of olefin to sulphuric acid is not substantially less than 1 and not substantially more than 2.

4. Process of claim 1 in which the molecular ratio of olefin to sulphuric acid is substantially 5. Process of claim 1 in which a portion of the reaction product is drawn off and the remaining portion recycled with the reactants.

6. Process of claim 1 in which at least oneoi the reactants is introduced at at least two points along the flow-path. y

7. Process for the preparation of alkyl sulphates, which comprises forcing a liquefied olefin and sulphuric acid of 75-100% concentration concurrently and continuously thru a fiow-path' of restricted cross-section while maintaining the temperature of reactants below 40 0., the reactants being forced thru said flow-path at a rate such that the reaction is substantially completed within said flow-path.

8. Process of preparingisopropyl sulphate,

which comprises forcing liquid propylene and sulphuric acid of 75-100% concentration in the molecular ratio'of substantially lzl concurrent- 1y andv continuously thru a. flow-path of restricted cross-section while maintaining the tempera- 5 ture of the reactants below 40 (1, the length of said flow-path being. adjusted so that the reaction is substantially completed withinsaid flowpath.

9. Process for the preparationof isopropyl sulphates which comprises passing a mixture of liquid propylene and sulphuric acid of -100'% concentration, through a flow-path of restricted cross-section maintained at -l0 to +40" C.,'the length of said flow-path being adjusted so that 15 the reaction is substantially completed within said flow-path.

10. Process for" the preparation ofisopropyl sulphates which comprises passing a mixture containing liquid propylene and sulphuric acid of 20 80100% concentration through va flow-path of restricted cross-section maintainedat 10-30 C., the length of said flow-path being adjusted so that the reaction is substantially completed within said flow-path. I

11. Process for the preparation of'isopropyl sulphates which comprises passing -a mixture containing 1 mol. of liquid propylene and 1 mol.

of 80- 100% sulphuric acid through a flow-path of restricted cross-section maintained at 10-30 30 C. the length 'ofsaid flow-path being adjusted so that the reaction is substantially completed witha in said flow-path.

12. Process for the preparation of isopropyl sulphates which comprises; passing a mixture containing 1 mol. of liquid propylene and 1 mol. of -95% sulphuric acid through a flow-path of restricted cross-section, which flow-path is maintained at 10-30 'C., the length of said-flowpath being adjusted so that the reaction is substantially completed within said flow-path.

13. Process for the preparation of isopropyl sulphates which comprises passing a mixture containing 1 mol. of liquid propylene and 1 mol. of 90-95% sulphuric acid through a flow-path of '"estricted cross-section wherein the flowing material is maintained at approximately 25 C.

HOWARD s. round. 

